A new approach is introduced for the calculation of multiphoton partial decay rates; in ionizing and dissociative processes. The partial decay rates (partial resonance widths) are calculated by carrying out asymptotic analysis of a complex scaled resonance quasienergy solution of the time-dependent Schrodinger equation obtained when the acceleration, momentum, reduced momentum, or length gauges are used. The partial width analysis is made only after applying the proper complex-scaled transformations on the resonance solution. The recently developed (t,t’) algorithm [J. Chem. Phys. 99, 4590 (1990)] significantly reduces the computational effort when the Hamiltonian is represented in the momentum gauge or in the length gauge. The new approach is applied to a model Hamiltonian which describes the multiphoton detachment of Cl- in the A(r)F laser field.